Embryo space colonization is a theoretical interstellar space colonization concept that involves sending a robotic mission to a habitable terrestrial planet transporting frozen early-stage human embryos or the technological or biological means to create human embryos. The proposal circumvents the most severe technological problems of other mainstream interstellar colonization concepts. In contrast to the sleeper ship proposal, it does not require the more technically challenging 'freezing' of fully developed humans (see cryonics). In addition, in contrast to both a sleeper ship and a generation ship the resources needed to build a spacecraft for an embryonic space colonization effort are considerably lower in terms of pure mass and complexity of the spacecraft. The concept is explored in the science fiction novel 'The Future Happens Twice'